Fluid Injection System

ABSTRACT

A fluid injection system having a line section in which an injection apparatus is arranged and having, arranged downstream thereof, an evaporator device to which there is assigned, downstream, a catalytic converter in which a fluid injected by the injection apparatus undergoes a catalytic reaction with the exhaust gas. At least one further injection apparatus is arranged in the line section.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of application No. PCT/EP2016/076106, filed on Oct. 28, 2016. Priority is claimed on German Application No. DE102015221360.9, filed Oct. 30, 2015, the content of which is incorporated here by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a fluid injection system having a line section in which an injection apparatus is arranged and arranged downstream thereof an evaporator device and a downstream catalytic converter in which a fluid injected by the injection apparatus undergoes a catalytic reaction with the exhaust gas.

2. Description of the Prior Art

It is known, for exhaust-gas aftertreatment, for an additive to be injected into the exhaust gas to minimize or convert undesired constituents of the exhaust gas. For this purpose, a line section arranged upstream of an evaporator device is equipped with an injection apparatus by which the additive is injected into the exhaust-gas stream. The efficiency of the exhaust-gas after treatment is in this case determined inter alia by the nature of the injection of the additive into the exhaust-gas stream. To achieve good mixing of the injected additive with the exhaust gas, the additive is injected at an angle with respect to the longitudinal axis of the line section. Good mixing of the additive with the exhaust-gas stream is necessary in order to realize a good droplet distribution at the evaporator device. It has nevertheless been found that an inhomogeneous droplet distribution is encountered at the evaporator device. The inhomogeneous droplet distribution gives rise to local cooling in the evaporator device, which promotes the formation of deposits in the evaporator device. This leads to reduced evaporator performance of the additive and thus to impaired exhaust-gas aftertreatment.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to create a fluid injection system that leads to as homogeneous as possible a droplet distribution in relation to the line cross section at the evaporator device.

According to one aspect of the invention, at least one further injection apparatus is arranged in a line section. The arrangement of at least one further injection apparatus makes it possible to generate an improved droplet distribution of the injected additive over the entire cross section of the line section, because each injection apparatus has to generate a uniform droplet distribution for only one sector of the cross section. The uniform droplet distribution in the individual sectors by each respective injection apparatuses produces a homogeneous droplet distribution over the entire line cross section.

In an advantageous embodiment, a very good homogeneous droplet distribution over the line cross section is achieved by virtue of just two injection apparatuses being arranged in the line section.

Depending on a size of the exhaust-gas aftertreatment unit and of a line cross section predefined thereby, it has proven to be advantageous for a maximum of four injection apparatuses to be arranged in the line section.

According to a further advantageous embodiment, the formation of a homogeneous droplet distribution over the entire cross section is achieved by virtue of the injection apparatuses being arranged symmetrically on a circumference of the line section.

For the formation of a homogeneous droplet distribution, it is necessary for the injection apparatuses to be aligned relative to one another. In a further embodiment, flawless alignment of the injection apparatuses relative to one another is achieved by virtue of the line section being composed of multiple line elements, wherein an injection apparatus is arranged in each line element. This embodiment permits the separate fastening and alignment of each individual injection apparatus on the line element assigned thereto. The completed line section is subsequently produced by assembling the individual line elements.

In a further embodiment, the injection apparatuses are arranged at a same level in a flow direction. This has the advantage that the line elements from which the line section is assembled are of identical construction.

Depending on the flow conditions of the exhaust gas and/or on the design of the line section, a homogeneous droplet distribution may not be achieved as a result of the merging of the spray patterns of the individual injection apparatuses. In these cases, in accordance with another advantageous embodiment, a homogeneous droplet distribution over the line cross section can be achieved by virtue of at least one injection apparatus being arranged downstream of at least one further injection apparatus. In this embodiment, too, the injection apparatuses arranged offset in the flow direction may be arranged so as to be distributed symmetrically on the circumference of the line section.

An arrangement of the injection apparatuses so as to be offset in the flow direction is also advantageous if the structural space surrounding the line section is restricted such that it is not possible for the injection apparatuses to be arranged at the same level in relation to the flow direction. Here, the existing structural space can be utilized particularly effectively if the injection apparatuses are arranged so as to be distributed asymmetrically, for example at intervals of 90°, on the circumference of the line section.

Here, it has proven to be advantageous if the spacing of the injection apparatuses in the flow direction amounts to between 0.1 to 1.5 times the diameter of the line section, preferably 0.2 to 1.0 times the diameter of the line section, and in particular 0.4 to 0.8 times the diameter of the line section.

In a particularly simple advantageous embodiment, the injection apparatuses are arranged at the same angle with respect to the longitudinal axis of the line section.

A particularly simple adaptation of the individual spray patterns of the injection apparatuses in order to achieve a homogeneous droplet distribution is achieved by virtue of at least one injection apparatus being arranged at a different angle with respect to the longitudinal axis of the line section than another injection apparatus.

In another advantageous embodiment, a homogeneous droplet distribution can be achieved by virtue of at least one injection apparatus generating a different spray pattern than the at least one other injection apparatus.

By these embodiments, it is possible to realize a homogeneous droplet distribution in the line cross section for a wide variety of lines and flow conditions of the exhaust gas.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail by way of an exemplary embodiment. In the drawings:

FIG. 1 is a fluid injection apparatus according to the invention;

FIGS. 2A and 2B are a sections through the fluid injection apparatus as per FIG. 1; and

FIGS. 3-6: are further arrangements of the injection apparatuses.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 shows an exhaust-gas aftertreatment unit in a motor vehicle, having a line section 1, an evaporator device 2, which is arranged downstream thereof, and which is assigned a downstream catalytic converter 3. The line section 1 is of substantially tubular form. Two protuberances 4 are arranged symmetrically on the circumference of the line section 1 and serve for accommodating in each case one injection apparatus 5, by which a urea solution is injected into an exhaust-gas stream flowing in the direction of the arrow. For this purpose, the urea solution is fed from an additive tank to the injection apparatuses 5 via feed lines 6 by a delivery unit (not illustrated). The protuberances 4 are adapted, in terms of quantity and direction, to the exhaust-gas stream and to the feed of urea solution. The line section 1 is composed of two line elements 7, 7′, which are connected to one another.

FIG. 2A shows a section through the line section 1 with the protuberances 4. The injection apparatuses are not illustrated; only injection jets 8, 8′ are shown. The injection apparatuses 5 are in this case designed such that a jet 8 as a core jet and a jet 8′ as an envelope jet surrounding the core jet are formed. The two jets 8, 8′ are thus formed such that, collectively, they cover the entire cross section of the line section 1, whereby an optimum feed of the urea solution into the exhaust-gas stream is realized.

The apparatus as per FIG. 2B differs merely in that the two jets 8, 8′ are injected at different angles, of β=15° and α=20°, with respect to the longitudinal axis of the line section 1.

The line section 1 in FIG. 3 is composed of three line elements 7, 7′, 7″, each with one injection apparatus 5. The line elements 7, 7′, 7″ are designed such that the injection apparatuses 5 are distributed symmetrically on the circumference of the line section 1. The injection apparatuses 5 are designed, with regard to the jet injection into the line section, such that each jet 8, 8′, 8″ has an approximately elliptical cross section. Aside from a central region 9, the jets 8, 8′, 8″ cover the entire cross section of the line section 1. The central region 9 not covered by the direct injection is in this case not critical, because a distribution of the jets 8, 8′, 8″ is realized by the exhaust-gas stream, such that the urea solution is distributed over the entire cross section and thus also into the central region 9.

An arrangement of four injection apparatuses 5 is illustrated in FIG. 4. The line section 1 is made up of two line elements 7, 7′, wherein two injection apparatuses 5 are arranged in each line element 7, 7′.

The fluid injection system in FIG. 5 has two injection apparatuses 5 in the line section 1, wherein said injection apparatuses are arranged one behind the other in the flow direction and at the same level in a circumferential direction. The spacing of the injection apparatuses 5 in the flow direction amounts to 1.5 times the diameter of the line section 1.

In FIG. 6, the injection apparatuses 5 are likewise arranged one behind the other in the flow direction. At the same time, the injection apparatuses 5 are arranged with a spacing of 180° in the circumferential direction. The spacing of the injection apparatuses 5 in the flow direction amounts to 0.5 times the diameter of the line section 1.

Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto. 

1.-10. (canceled)
 11. A fluid injection system comprising: a line section; a first injection apparatus arranged in the line section and configured to inject a fluid; and at least one further injection apparatus is arranged in the line section and configured to inject the fluid, wherein the line section is configured to have a downstream evaporator device and downstream thereof a catalytic converter in which the fluid injected by the injection apparatuses undergoes a catalytic reaction with exhaust gas.
 12. The fluid injection system as claimed in claim 11, wherein at most four injection apparatuses are arranged in the line section.
 13. The fluid injection system as claimed in claim 12, wherein the injection apparatuses are arranged symmetrically on a circumference of the line section.
 14. The fluid injection system as claimed in claim 12, wherein the line section comprises multiple line element segments, wherein at least one injection apparatus is arranged in each line element.
 15. The fluid injection system as claimed in claim 11, wherein the injection apparatuses are arranged at a same level in a flow direction.
 16. The fluid injection system as claimed in at claim 11, wherein at least one injection apparatus is arranged downstream of the at least one further injection apparatus.
 17. The fluid injection system as claimed in claim 16, wherein a spacing of the injection apparatuses in a flow direction is between at least one of: 0.1 to 1.5 times a diameter of the line section, 0.2 to 1.0 times the diameter of the line section, and 0.4 to 0.8 times the diameter of the line section.
 18. The fluid injection system as claimed claim 12, wherein the injection apparatuses are arranged at a same angle with respect to a longitudinal axis of the line section.
 19. The fluid injection system as claimed in claim 12, wherein at least one injection apparatus is arranged at a different angle with respect to a longitudinal axis of the line section than another injection apparatus.
 20. The fluid injection system as claimed in claim 12, wherein at least one injection apparatus generates a different spray pattern than at least one other injection apparatus. 